Saudi Arabia's investigation and handling of the murder of journalist Jamal Khashoggi still lacks full credibility and accountability, a senior US official said Friday.

Secretary of State Mike Pompeo will continue to press the Saudis on Khashoggi's murder when he visits Riyadh next week as part of an eight-country tour of the Middle East, the official said.

"He will raise the case of journalist Jamal Khashoggi and continue to push for accountability and credibility from the Saudi leadership as they move through the legal process that began earlier this week," the official told journalists on condition of anonymity.

"I don't think, from our point of view, that the narrative emerging from the Saudis throughout the legal process has yet hit that threshold of credibility and accountability," the official said.

In a case that shocked the world and created a sharp rift with Washington, Khashoggi was murdered and his corpse dismembered inside the kingdom's Istanbul consulate on October 2.

After evidence emerged that the killing was done by a team of Saudis sent from Riyadh and closely linked to Crown Prince Mohammed bin Salman, Washington demanded a transparent investigation.

On November 15, Riyadh prosecutors announced indictments against 11 people, and on Tuesday prosecutors said they were seeking the death penalty against five of them.

But at the same time Prince Mohammed, whose right-hand aides were allegedly involved in the murder, was exonerated despite US intelligence reportedly having evidence that he was behind it.

Despite the indictments so far, it was not clear if anyone in Prince Mohammed's close orbit would be charged.

The case has made it difficult for the Trump administration to return the crucial bilateral relationship back to normal.

A bipartisan resolution approved by the US Senate last month also held the crown prince responsible for the killing.

"The Saudis should have a credible narrative for what happened in the consulate and subsequent events," the US official said Friday.

"It's in their interest to pursue this as aggressively as they can to get this albatross off their backs and to get out from under the shadow of this incident, which has caused such an outcry."